How the record chills we remember are now somehow less cold?
So quite a bit of fuse has been made about wind chills over the past week including some conversations about breaking records. The problem with our wind chill index today and comparing it to wind chills from even 1996 when we had that last major super blast of OMG cold, is that the formula that the weather service uses to figure wind chills was changed in 2001. So how can we compare the wind chills of the past with our current conditions if the data is not the same? We have been comparing apples to oranges during this whole ordeal!
NOAA, or as we call them the National Weather Service explains the change on their website.
“In late 2001, the National Weather Service implemented a new Wind Chill Temperature (WCT) Index. The reason for the change was to improve upon the old index used by the NWS and the Meteorological Services of Canada (MSC) which was based on the 1945 Siple and Passel Index.
The new Wind Chill/Temperature Index makes use of advances in meteorology, biometeorology and computer modeling to provide a more accurate, useful formula for calculating the dangers from winter winds and freezing temperatures. In addition, clinical trials have been conducted and the results of those trials have been used to verify and improve the accuracy of the new formula.
Led by the NWS, implementation of the standarized WCT Index took place throughout the nation and involved the entire meteorological community, and the media, which plays an important role in explaining the index to the general public. In this way, an accurate and consistent measure has been provided to help the public protect itself against the dangers of frostbite and hypothermia. The index has been implemented in Canada and the United States in order to have a consistent WCT Index for North America.”
https://www.weather.gov/oun/safety-winter-windchill
Let take Tuesday night in Brainerd for an example. The Brainerd Airport is where the official weather reporting station is for the weather service. At around 10pm on Tuesday, January 29th, 2019 the air temperature was -29F. The wind was from the northwest at 16mph and the wind chill as figured using the new post 2001 formula was -57F, which is very cold. However, when you use the old formula it’s worse! The old way of figuring wind chill had it at -72F!!!
So did we break a record or not?
To find the definitive answer I contacted our National Weather service office in Duluth, MN and spoke with Observation Program Leader, Steve Gohde. He told me that they have taken all of the old data and the records have been recalculated using the new method for a fair comparison. The wind chills of our 1996 cold snap were in fact still colder. They have taken those stats from 1996 and figured them using the new calculation. February 1, 1996 wind chill adjusted for the new conversion was -66. February 2, 1996 was also colder at -65.
As impressive as the thought of breaking the record for Brainerd is, we did not.